This invention relates to a gear shift control for automatic transmissions in motor vehicles having an electronic control unit and, more particularly, to a gear shift control for automatic transmissions in motor vehicles having an electronic control unit which determines the gear change as a function of operating parameters of the vehicle.
A known gear shift control is described, for example, in the ATZ article "The Adaptive Transmission Control for the Automatic Transmission of BMW Vehicles with a 12-Cylinder Engine", September 1992, Page 428+. For the gear shift control, the electronic control unit receives as input signals a plurality of operating parameters of the vehicle, such as the throttle valve angle, the driving speed, the rotational wheel speeds, the engine drive torque, the longitudinal acceleration as well as the lateral acceleration of the vehicle, the rotational engine speed and the rotational output speed. The adaptive transmission control carries out a driver-adapted and situation-adapted gear shift control also by means of the so-called "driver type recognition", "environment recognition" and "driving situation recognition". By means of the "driver type recognition", it is determined as a function of operating parameters which reflect the driver's intention whether a more economical or a sportier driving method is desired. By means of the function blocks "environment recognition" and "driving situation recognition", environmental conditions are determined as a function of operating parameters of the vehicle which exist indirectly with a high probability, such as a slippery road, uphill or downhill driving, cornering or a stop-and-go operation. For the gear shift control, different shifting programs in the form of characteristic upshift and downshift curves are available which are activated, for example, as a function of the "driver type recognition" or of the "environment recognition". The gear shift control is basically carried out corresponding to the respective selected shifting program. However, for example, as a function of the result of the so-called "driving situation recognition", it can be changed by additional functions, such as an upshift suppression, a downshift suppression or an immediate triggering of a downshifting.
However, this known gear shift control achieves a situation-adapted driving method only for a short time for a driving situation which has already occurred and which is determined by operating parameters of the vehicle in each case only for the momentary point in time. In the event of frequently changing operating parameters of the vehicle, an unintentional increase of the shifting frequency and, therefore, a reduction of the comfort, may occur as the result of this momentary adaption. Also, an environmental condition (for example, stop-and-go traffic) determined indirectly by operating parameters does not actually exist with absolute certainty or exists only for a very short period of time.
There is therefore needed an improved gear shift control of the above-mentioned type such that an optimization of the comfort is achieved, particularly by the reduction of the shifting frequency, by a better assignment of an intervention and by the actual driving situation conditions. Hence, a reduction of the necessary driver interventions is achieved. Furthermore, preferably the fuel consumption is to be reduced and the driving safety is to be increased.
These needs are met according to the present invention by a gear shift control for automatic transmissions in motor vehicles, having an electronic control unit which determines the gear change as a function of operating parameters of the vehicle. The electronic control unit controls the gear changes also as a function of input signals which are obtained from information generated outside the vehicle and reflect the environmental conditions of the vehicle.
According to the invention, the electronic control unit controls the gear shifting also as a function of input signals which are received from information developed outside the vehicle and reflect the environmental conditions of the vehicle.
Information concerning environmental conditions of the vehicle developed outside the vehicle are provided, for example, by satellite networks (GPS), radio data systems (RDS, European Radio Data System) mobile radio units, electronic traffic signs and/or maps with street and location markings digitally stored for vehicle navigation systems. In addition, it is conceivable to detect corresponding information also by means of optical sensors and to make them available in the vehicle by means of image processing. All information can, for example, be received by a central unit, such as a navigation system, existing in the vehicle and can be transmitted to the electronic control unit. However, it is also possible to construct the electronic control unit such that it can itself receive and process the information.
This information, which is available independently of the vehicle, and concerns the environmental conditions within which the vehicle is moving, permits a longer-term recognition of the driving situation which is independent of very rapidly changing operating parameters of the vehicle, and therefore a more stable gear shift control. In the following, this operation will be explained by an example:
When an electronic traffic sign provides the information that a downhill drive from a pass follows which has a length of 30 km, a corresponding conclusion can be drawn with respect to a fairly long-lasting environmental condition "downhill drive" for the indicated distance, in the case of which short sections without any slope are ignored. If, according to the prior art, the downhill drive were detected via the operating parameters of the vehicle, particularly by a gradient indicator or by the comparison of the vehicle acceleration and the throttle valve angle, the end of the downhill drive would, in each case, be recognized on the short section without any slope. Then, a corresponding change of the gear shift control strategy would normally result in an upshifting. In the section which follows and which is sloped again, a downhill drive would again be recognized. Correspondingly, the gear shift control strategy will be changed again and, for example, a downshifting is caused. Therefore, in the case of a "downhill drive" recognition as a function of the operating parameters of the vehicle, a pendulum shifting is possible which reduces the comfort in the vehicle.
Preferably, the input signals also reflect environmental conditions to be expected in the future.
The optimal gear relative to a newly occurring situation is therefore not engaged in a delayed manner, but rather the driving method can already be adapted with, or before, the occurrence of a driving situation or environmental condition to be expected. In addition, by anticipating the indication of the environmental conditions of the vehicle to be expected, it can be recognized whether a frequent change of driving situations exists with constantly recurring environmental conditions. In this case, it can be determined by statistical analysis which environmental conditions are to be expected most frequently, and then the method of operation adapted to this environmental condition can be maintained also in the case of short-term changes of the environmental condition.
Accordingly, by using the gear shift control according to the invention, the shifting frequency is reduced and the driving method is adapted early and/or in an anticipating manner to a longer-lasting driving situation.
It is an advantage of the invention that an input signal reflects the type of the road on which the vehicle is situated. Adapted to the type of road, the gear shift control can take measures for reducing the shifting frequency, for example, in the case of a multiple-curve country road; or measures for reducing the exhaust gas emissions, for example, in city driving. As the result of the type of road, a plurality of driving situations can be recognized in an anticipating manner, such as downhill driving, uphill driving, cornering and straight-ahead driving. The type of road is available as information via the stored map in the case of navigation systems for motor vehicles or by means of electronic traffic signs. The type of road can be indicated by its category (for example, autobahn, country road, city street); by its cornering profiles, slope profiles and gradient profiles; or by its road condition (for example, track grooves, gravel, tar).
According to a further advantage of the invention, an input signal reflects the traffic situation at least on the road on which the vehicle is situated. Information concerning the traffic situation is available, for example, by means of the known radio data systems (RDS). As a function of the traffic situation, the shifting frequency can be reduced, for example, for increasing the comfort in the case of a sluggish traffic, or the driving safety can be increased, for example, by means of a downshifting, for reducing the driving speed in the event of an accident danger.
According to a still further advantage of the invention, an input signal reflects the weather situation in the close vicinity of the road on which the vehicle is situated. Information concerning the weather situation is also available from the radio data system RDS. As a result of the information regarding the weather situation, the driving method can be adapted via the gear shift control, particularly for increasing the driving safety. For example, in the case of a slippery road, preferably higher gears can be permitted and/or the lowest gears can be prohibited. As a result of the information of the weather situation as an input signal for the electronic control unit, particularly the directional control of the vehicle can therefore be increased.
According to yet another advantage of the invention, an input signal indicates a location marking in the close vicinity of the road on which the vehicle is situated. Such information is provided by the maps stored in navigation systems or also by the known radio data systems RDS.
When it is recognized that the vehicle is situated, for example, in a zone endangered by smog, for minimizing the exhaust gas emissions, the gear shift control can take place corresponding to the shifting program by which the lowest fuel consumption is achieved. Thus, by using the gear shift control according to the invention, the driving method can also be adapted to environmental protection requirements.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.